GEOLOGICAL HISTORY OF COCKROACHES 



245 



recent cockroaches. The thick arched front wing with strongly de- 

 limited anal area dates from the Carboniferous. The group, however, 

 has by no means remained stationary since the Carboniferous. On the 

 contrary, close observation reveals evidence of advance along distinct 

 and definite lines. The Carboniferous cockroaches are provided with 

 a long ovipositor resembling that of the katydids or crickets; modern 

 cockroaches have a reduced and specialized ovipositor. Early cock- 

 roaches no doubt deposited their eggs in the ground or under the 

 bark of trees or within the tissue of succulent stems; modern forms 

 deposit their eggs in a very characteristic egg case. The front wings 



Fig. 1. Front wing of a typ- 

 ical Coal Measure cockroach, 

 (Jerablallina arcuata Sellards. 

 1, costa; 2, sub costa ; 3, radius 1 

 4, media; 5, cubitus; 6, anal 

 veins. Twice natural size. Au- 

 thor's illustration. 



Fig. 3. Front wing ot 

 a modern cockroach, Ec- 

 lobia germanica, X 5- 

 Original drawing. 



Fig. 2. Front wins of a Per- 

 mian cockroach, X'n. Original 

 drawing. Gn. sp. new. Au- 

 thor's Mns. 



From a comparison of the three typfs, Carboniferous (oldest), Permian (later), and (Fig. 3) 

 modern, it is seen that: the wing has become increasingly slender and compact; the main 

 veins have become partly fused ; cross veins have developed, and the direction of the anal 

 veins has changed. 



have become in general more resistant, the venation more complicated. 

 The hind wings have developed plications and a longitudinal fold. 

 The value to biology of a study of the group is in direct proportion 

 to the completeness with which these changes and the laws governing 

 them can be traced out. 



The wing of a typical cockroach of Carboniferous time is of simple 

 structure. A border vein, the costa, traverses and strengthens the 

 costal border. Four strong veins arising close together near the base 

 of the wing diverge and supply the greater part of the wing membrane. 

 The first of these, the subcosta, meets the costal border about or be- 

 yond the middle length of the wing; numerous superior branches are 



